In or out?

   I took this picture at the Presidio in San Francisco. The body of water you see here, called Crissy Field Marsh, often has some interesting wildlife in or near it, so I was looking for these things as I walked by it earlier today, when this unusual sight caught my eye. I looked at it first at the angle that you see here, then walked past it to get a better look at what was there to see. I was trying to determine, firstly, if the chain attached to the small metal pole sticking out of the ground was actually attached to the large wood trunk, and secondly, why it would be attached at all, which it was.
   It initially looked to me like a piece of art, a sculpture, because it didn't appear to have any other reason for being than that. I then thought about it a bit more, and realized that it must have some other relation, though it's not at all clear to me what that is, which is why I'm writing about it here.
   Is that small chain and pole trying to somehow hold that large object, trying to keep it from ending up in the marsh? Or maybe it's like a boat's life ring, giving the trunk something to grab on to, though it has no arms (the wood actually is shaped a bit like a four-legged animal's trunk with severed limbs). I looked around me and saw many dogs both on and off leashes, and wondered if it wasn't a bit like a pet.
   After ruminating more about what is in the picture and writing about it here, I'm still not really any closer to understanding what I see; possible meanings come and go in and out, and it's this quality of mystery that I find so moving in the world of objects.
   Come to think of it, I think it may be the very type of art that moves me after all.